diff --git a/.travis.yml b/.travis.yml index 2e0ad87affbcf2..185846029c2d8b 100644 --- a/.travis.yml +++ b/.travis.yml @@ -56,7 +56,7 @@ matrix: ./venv/bin/python -m test.pythoninfo script: # Skip tests that re-run the entire test suite. - - ./venv/bin/python -m coverage run --pylib -m test --fail-env-changed -uall,-cpu -x test_multiprocessing_fork -x test_multiprocessing_forkserver -x test_multiprocessing_spawn + - ./venv/bin/python -m coverage run --pylib -m test --fail-env-changed -uall,-cpu -x test_multiprocessing_fork -x test_multiprocessing_forkserver -x test_multiprocessing_spawn -x test_concurrent_futures after_script: # Probably should be after_success once test suite updated to run under coverage.py. # Make the `coverage` command available to Codecov w/ a version of Python that can parse all source files. - source ./venv/bin/activate diff --git a/Doc/library/concurrent.futures.rst b/Doc/library/concurrent.futures.rst index d85576b8bedd8e..30556fbb345490 100644 --- a/Doc/library/concurrent.futures.rst +++ b/Doc/library/concurrent.futures.rst @@ -191,13 +191,16 @@ that :class:`ProcessPoolExecutor` will not work in the interactive interpreter. Calling :class:`Executor` or :class:`Future` methods from a callable submitted to a :class:`ProcessPoolExecutor` will result in deadlock. -.. class:: ProcessPoolExecutor(max_workers=None) +.. class:: ProcessPoolExecutor(max_workers=None, mp_context=None) An :class:`Executor` subclass that executes calls asynchronously using a pool of at most *max_workers* processes. If *max_workers* is ``None`` or not given, it will default to the number of processors on the machine. If *max_workers* is lower or equal to ``0``, then a :exc:`ValueError` will be raised. + *mp_context* can be a multiprocessing context or None. It will be used to + launch the workers. If *mp_context* is ``None`` or not given, the default + multiprocessing context is used. .. versionchanged:: 3.3 When one of the worker processes terminates abruptly, a @@ -205,6 +208,10 @@ to a :class:`ProcessPoolExecutor` will result in deadlock. was undefined but operations on the executor or its futures would often freeze or deadlock. + .. versionchanged:: 3.7 + The *mp_context* argument was added to allow users to control the + start_method for worker processes created by the pool. + .. _processpoolexecutor-example: diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py index 50ee296ac89b78..67ebbf515215cd 100644 --- a/Lib/concurrent/futures/process.py +++ b/Lib/concurrent/futures/process.py @@ -50,8 +50,7 @@ from concurrent.futures import _base import queue from queue import Full -import multiprocessing -from multiprocessing import SimpleQueue +import multiprocessing as mp from multiprocessing.connection import wait import threading import weakref @@ -74,11 +73,11 @@ # threads/processes finish. _threads_queues = weakref.WeakKeyDictionary() -_shutdown = False +_global_shutdown = False def _python_exit(): - global _shutdown - _shutdown = True + global _global_shutdown + _global_shutdown = True items = list(_threads_queues.items()) for t, q in items: q.put(None) @@ -158,12 +157,10 @@ def _process_worker(call_queue, result_queue): This worker is run in a separate process. Args: - call_queue: A multiprocessing.Queue of _CallItems that will be read and + call_queue: A ctx.Queue of _CallItems that will be read and evaluated by the worker. - result_queue: A multiprocessing.Queue of _ResultItems that will written + result_queue: A ctx.Queue of _ResultItems that will written to by the worker. - shutdown: A multiprocessing.Event that will be set as a signal to the - worker that it should exit when call_queue is empty. """ while True: call_item = call_queue.get(block=True) @@ -180,6 +177,11 @@ def _process_worker(call_queue, result_queue): result_queue.put(_ResultItem(call_item.work_id, result=r)) + # Liberate the resource as soon as possible, to avoid holding onto + # open files or shared memory that is not needed anymore + del call_item + + def _add_call_item_to_queue(pending_work_items, work_ids, call_queue): @@ -231,20 +233,21 @@ def _queue_management_worker(executor_reference, executor_reference: A weakref.ref to the ProcessPoolExecutor that owns this thread. Used to determine if the ProcessPoolExecutor has been garbage collected and that this function can exit. - process: A list of the multiprocessing.Process instances used as + process: A list of the ctx.Process instances used as workers. pending_work_items: A dict mapping work ids to _WorkItems e.g. {5: <_WorkItem...>, 6: <_WorkItem...>, ...} work_ids_queue: A queue.Queue of work ids e.g. Queue([5, 6, ...]). - call_queue: A multiprocessing.Queue that will be filled with _CallItems + call_queue: A ctx.Queue that will be filled with _CallItems derived from _WorkItems for processing by the process workers. - result_queue: A multiprocessing.Queue of _ResultItems generated by the + result_queue: A ctx.SimpleQueue of _ResultItems generated by the process workers. """ executor = None def shutting_down(): - return _shutdown or executor is None or executor._shutdown_thread + return (_global_shutdown or executor is None + or executor._shutdown_thread) def shutdown_worker(): # This is an upper bound @@ -254,7 +257,7 @@ def shutdown_worker(): # Release the queue's resources as soon as possible. call_queue.close() # If .join() is not called on the created processes then - # some multiprocessing.Queue methods may deadlock on Mac OS X. + # some ctx.Queue methods may deadlock on Mac OS X. for p in processes.values(): p.join() @@ -377,13 +380,15 @@ class BrokenProcessPool(RuntimeError): class ProcessPoolExecutor(_base.Executor): - def __init__(self, max_workers=None): + def __init__(self, max_workers=None, mp_context=None): """Initializes a new ProcessPoolExecutor instance. Args: max_workers: The maximum number of processes that can be used to execute the given calls. If None or not given then as many worker processes will be created as the machine has processors. + mp_context: A multiprocessing context to launch the workers. This + object should provide SimpleQueue, Queue and Process. """ _check_system_limits() @@ -394,17 +399,20 @@ def __init__(self, max_workers=None): raise ValueError("max_workers must be greater than 0") self._max_workers = max_workers + if mp_context is None: + mp_context = mp.get_context() + self._mp_context = mp_context # Make the call queue slightly larger than the number of processes to # prevent the worker processes from idling. But don't make it too big # because futures in the call queue cannot be cancelled. - self._call_queue = multiprocessing.Queue(self._max_workers + - EXTRA_QUEUED_CALLS) + queue_size = self._max_workers + EXTRA_QUEUED_CALLS + self._call_queue = mp_context.Queue(queue_size) # Killed worker processes can produce spurious "broken pipe" # tracebacks in the queue's own worker thread. But we detect killed # processes anyway, so silence the tracebacks. self._call_queue._ignore_epipe = True - self._result_queue = SimpleQueue() + self._result_queue = mp_context.SimpleQueue() self._work_ids = queue.Queue() self._queue_management_thread = None # Map of pids to processes @@ -426,23 +434,23 @@ def weakref_cb(_, q=self._result_queue): # Start the processes so that their sentinels are known. self._adjust_process_count() self._queue_management_thread = threading.Thread( - target=_queue_management_worker, - args=(weakref.ref(self, weakref_cb), - self._processes, - self._pending_work_items, - self._work_ids, - self._call_queue, - self._result_queue)) + target=_queue_management_worker, + args=(weakref.ref(self, weakref_cb), + self._processes, + self._pending_work_items, + self._work_ids, + self._call_queue, + self._result_queue)) self._queue_management_thread.daemon = True self._queue_management_thread.start() _threads_queues[self._queue_management_thread] = self._result_queue def _adjust_process_count(self): for _ in range(len(self._processes), self._max_workers): - p = multiprocessing.Process( - target=_process_worker, - args=(self._call_queue, - self._result_queue)) + p = self._mp_context.Process( + target=_process_worker, + args=(self._call_queue, + self._result_queue)) p.start() self._processes[p.pid] = p diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py index e4c9ace9356615..ed8ad41f8e6cb5 100644 --- a/Lib/test/test_concurrent_futures.py +++ b/Lib/test/test_concurrent_futures.py @@ -19,6 +19,7 @@ from concurrent.futures._base import ( PENDING, RUNNING, CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED, Future) from concurrent.futures.process import BrokenProcessPool +from multiprocessing import get_context def create_future(state=PENDING, exception=None, result=None): @@ -56,6 +57,15 @@ def my_method(self): pass +class EventfulGCObj(): + def __init__(self, ctx): + mgr = get_context(ctx).Manager() + self.event = mgr.Event() + + def __del__(self): + self.event.set() + + def make_dummy_object(_): return MyObject() @@ -77,7 +87,13 @@ def setUp(self): self.t1 = time.time() try: - self.executor = self.executor_type(max_workers=self.worker_count) + if hasattr(self, "ctx"): + self.executor = self.executor_type( + max_workers=self.worker_count, + mp_context=get_context(self.ctx)) + else: + self.executor = self.executor_type( + max_workers=self.worker_count) except NotImplementedError as e: self.skipTest(str(e)) self._prime_executor() @@ -107,8 +123,29 @@ class ThreadPoolMixin(ExecutorMixin): executor_type = futures.ThreadPoolExecutor -class ProcessPoolMixin(ExecutorMixin): +class ProcessPoolForkMixin(ExecutorMixin): + executor_type = futures.ProcessPoolExecutor + ctx = "fork" + + def setUp(self): + if sys.platform == "win32": + self.skipTest("require unix system") + super().setUp() + + +class ProcessPoolSpawnMixin(ExecutorMixin): + executor_type = futures.ProcessPoolExecutor + ctx = "spawn" + + +class ProcessPoolForkserverMixin(ExecutorMixin): executor_type = futures.ProcessPoolExecutor + ctx = "forkserver" + + def setUp(self): + if sys.platform == "win32": + self.skipTest("require unix system") + super().setUp() class ExecutorShutdownTest: @@ -124,9 +161,17 @@ def test_interpreter_shutdown(self): from concurrent.futures import {executor_type} from time import sleep from test.test_concurrent_futures import sleep_and_print - t = {executor_type}(5) - t.submit(sleep_and_print, 1.0, "apple") - """.format(executor_type=self.executor_type.__name__)) + if __name__ == "__main__": + context = '{context}' + if context == "": + t = {executor_type}(5) + else: + from multiprocessing import get_context + context = get_context(context) + t = {executor_type}(5, mp_context=context) + t.submit(sleep_and_print, 1.0, "apple") + """.format(executor_type=self.executor_type.__name__, + context=getattr(self, "ctx", ""))) # Errors in atexit hooks don't change the process exit code, check # stderr manually. self.assertFalse(err) @@ -194,7 +239,7 @@ def test_thread_names_default(self): t.join() -class ProcessPoolShutdownTest(ProcessPoolMixin, ExecutorShutdownTest, BaseTestCase): +class ProcessPoolShutdownTest(ExecutorShutdownTest): def _prime_executor(self): pass @@ -233,6 +278,22 @@ def test_del_shutdown(self): call_queue.join_thread() +class ProcessPoolForkShutdownTest(ProcessPoolForkMixin, BaseTestCase, + ProcessPoolShutdownTest): + pass + + +class ProcessPoolForkserverShutdownTest(ProcessPoolForkserverMixin, + BaseTestCase, + ProcessPoolShutdownTest): + pass + + +class ProcessPoolSpawnShutdownTest(ProcessPoolSpawnMixin, BaseTestCase, + ProcessPoolShutdownTest): + pass + + class WaitTests: def test_first_completed(self): @@ -352,7 +413,17 @@ def future_func(): sys.setswitchinterval(oldswitchinterval) -class ProcessPoolWaitTests(ProcessPoolMixin, WaitTests, BaseTestCase): +class ProcessPoolForkWaitTests(ProcessPoolForkMixin, WaitTests, BaseTestCase): + pass + + +class ProcessPoolForkserverWaitTests(ProcessPoolForkserverMixin, WaitTests, + BaseTestCase): + pass + + +class ProcessPoolSpawnWaitTests(ProcessPoolSpawnMixin, BaseTestCase, + WaitTests): pass @@ -440,7 +511,19 @@ class ThreadPoolAsCompletedTests(ThreadPoolMixin, AsCompletedTests, BaseTestCase pass -class ProcessPoolAsCompletedTests(ProcessPoolMixin, AsCompletedTests, BaseTestCase): +class ProcessPoolForkAsCompletedTests(ProcessPoolForkMixin, AsCompletedTests, + BaseTestCase): + pass + + +class ProcessPoolForkserverAsCompletedTests(ProcessPoolForkserverMixin, + AsCompletedTests, + BaseTestCase): + pass + + +class ProcessPoolSpawnAsCompletedTests(ProcessPoolSpawnMixin, AsCompletedTests, + BaseTestCase): pass @@ -540,7 +623,7 @@ def test_default_workers(self): (os.cpu_count() or 1) * 5) -class ProcessPoolExecutorTest(ProcessPoolMixin, ExecutorTest, BaseTestCase): +class ProcessPoolExecutorTest(ExecutorTest): def test_killed_child(self): # When a child process is abruptly terminated, the whole pool gets # "broken". @@ -595,6 +678,34 @@ def test_traceback(self): self.assertIn('raise RuntimeError(123) # some comment', f1.getvalue()) + def test_ressources_gced_in_workers(self): + # Ensure that argument for a job are correctly gc-ed after the job + # is finished + obj = EventfulGCObj(self.ctx) + future = self.executor.submit(id, obj) + future.result() + + self.assertTrue(obj.event.wait(timeout=1)) + + +class ProcessPoolForkExecutorTest(ProcessPoolForkMixin, + ProcessPoolExecutorTest, + BaseTestCase): + pass + + +class ProcessPoolForkserverExecutorTest(ProcessPoolForkserverMixin, + ProcessPoolExecutorTest, + BaseTestCase): + pass + + +class ProcessPoolSpawnExecutorTest(ProcessPoolSpawnMixin, + ProcessPoolExecutorTest, + BaseTestCase): + pass + + class FutureTests(BaseTestCase): def test_done_callback_with_result(self): diff --git a/Misc/NEWS.d/next/Library/2017-09-22-16-02-00.bpo-31540.ybDHT5.rst b/Misc/NEWS.d/next/Library/2017-09-22-16-02-00.bpo-31540.ybDHT5.rst new file mode 100644 index 00000000000000..0b4259f88473bc --- /dev/null +++ b/Misc/NEWS.d/next/Library/2017-09-22-16-02-00.bpo-31540.ybDHT5.rst @@ -0,0 +1,4 @@ +Allow passing a context object in +:class:`concurrent.futures.ProcessPoolExecutor` constructor. +Also, free job ressources in :class:`concurrent.futures.ProcessPoolExecutor` +earlier to improve memory usage when a worker waits for new jobs.